Researcher:
Çem, Emrah

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Emrah

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Çem

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Çem, Emrah

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2009 - 200912010 - 20145

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Researcher Of Publications: search.filters.isAuthorOfPublication.cc335266-b9a0-47d8-a48d-cc64e11fc81e

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Now showing 1 - 6 of 6
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    Flat and hierarchical epidemics in P2P systems: energy cost models and analysis
    (Elsevier, 2014) N/A; Department of Computer Engineering; N/A; N/A; Department of Computer Engineering; Özkasap, Öznur; Çem, Emrah; Cebeci, Sena Efsun; Koç, Tuğba; Faculty Member; PhD Student; PhD Student; Researcher; Department of Computer Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; 113507; N/A; N/A; N/A
    In large scale distributed systems, epidemic or gossip-based communication mechanisms are preferred for their ease of deployment, simplicity, robustness against failures, load-balancing and limited resource usage. Although they have extensive applicability, there is no prior work on developing energy cost models for epidemic distributed mechanisms. In this study, we address power awareness features of two main groups of epidemics, namely flat and hierarchical. We propose a dominating-set based and power-aware hierarchical epidemic approach that eliminates a significant number of peers from gossiping. To the best of our knowledge, using a dominating set to build a hierarchy for epidemic communication and provide energy efficiency in P2P systems is a novel approach. We develop energy cost model formulations for flat and hierarchical epidemics. In contrast to the prior works, our study is the first one that proposes energy cost models for generic peers using epidemic communication, and examines the effect of protocol parameters to characterize energy consumption. As a case study protocol, we use our epidemic protocol ProFID for frequent items discovery in P2P systems. By means of extensive large scale simulations on PeerSim, we analyze the effect of protocol parameters on energy consumption, compare flat and hierarchical epidemic approaches for efficiency, scalability, and applicability as well as investigate their resilience under realistic churn.
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    Energy efficient hierarchical epidemics in peer-to-peer systems
    (IEEE, 2011) N/A; Department of Computer Engineering; Özkasap, Öznur; Çem, Emrah; Koç, Tuğba; Faculty Member; PhD Student; Master Student; Department of Computer Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 113507; N/A; N/A
    Epidemic or gossip-based mechanisms are preferred in several distributed protocols for their ease of deployment, simplicity, robustness against failures, load-balancing and limited resource usage. In flat neighborhood epidemics, peers have similar responsibilities and all participate in gossiping via neighboring peers. We have proposed an energy cost model for a generic peer using flat neighborhood epidemics, and examined the effect of protocol parameters to characterize energy consumption. Although it has been shown that a peers power consumption amount is independent of population size, peers always need to be active to process incoming gossip messages. In this study, we consider power awareness features of flat and hierarchical epidemics in peer-to-peer (P2P) systems, and propose a power-aware hierarchical epidemic approach with its energy cost model and analysis. In this adaptive approach, only a subset of peer population is active in gossiping by forming an overlay, so that the other peers can switch to idle state. It also allows data aggregation that can be utilized to reduce gossip message size. As a case study for epidemic protocol, we use our approach and simulation model for frequent item set discovery in unstructured P2P networks.
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    A distributed approach for computing sum aggregation in P2P networks
    (IEEE, 2011) N/A; Department of Computer Engineering; N/A; Özkasap, Öznur; Çem, Emrah; Faculty Member; PhD Student; Department of Computer Engineering; College of Engineering; Graduate School of Sciences and Engineering; 113507; N/A
    Since hand vein patterns are assumed not to change over time except in size and they are unique to each individual, researchers aim to construct a biometric control system based on hand vein patterns. Each hand vein pattern defines a graph structure. According to this, we converted each hand vein pattern to a graph and to match these graphs, we developed an algorithm based on (Graph Edit Distance) GED. GED is defined as the least cost graph edit operation sequence which is used to transform one graph to another. Our initial results confirm the utility of GED-based hand vein verification.
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    Energy cost model for frequent item set discovery in unstructured P2P networks
    (Springer, 2012) Demirkaya, Ender; N/A; N/A; N/A; Department of Computer Engineering; Çem, Emrah; Esiner, Ertem; Özaydın, Burak; Özkasap, Öznur; PhD Student; Master Student; Master Student; Faculty Member; Department of Computer Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; N/A; N/A; N/A; 113507
    For large scale distributed systems, designing energy efficient protocols and services has become as significant as considering conventional performance criteria like scalability, reliability, fault-tolerance and security. We consider frequent item set discovery problem in this context. Although it has attracted attention due to its extensive applicability in diverse areas, there is no prior work on energy cost model for such distributed protocols. In this paper, we develop an energy cost model for frequent item set discovery in unstructured P2P networks. To the best of our knowledge, this is the first study that proposes an energy cost model for a generic peer using gossip-based communication. As a case study protocol, we use our gossip-based approach ProFID for frequent item set discovery. After developing the energy cost model, we examine the effect of protocol parameters on energy consumption using our simulation model on PeerSim and compare push pull method of ProFID with the well-known push-based gossiping approach. Based on the analysis results, we reformulate the upper bound for the peer's energy cost.
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    Stepwise fair-share buffering for gossip-based peer-to-peer data dissemination
    (Elsevier, 2009) Ahi, Emrah; Department of Computer Engineering; Department of Mathematics; N/A; N/A; N/A; Özkasap, Öznur; Çağlar, Mine; Çem, Emrah; İskender, Emre; Faculty Member; Faculty Member; PhD Student; Master Student; Department of Computer Engineering; Department of Mathematics; College of Engineering; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 113507; 105132; N/A; N/A
    We consider buffer management in support of large-scale gossip-based peer-to-peer data dissemination protocols. Coupled with an efficient buffering mechanism, system-wide buffer usage can be optimized while providing reliability and scalability in such protocols. We propose a novel approach, stepwise fair-share buffering, that provides uniform load distribution and reduces the overall buffer usage where every peer has a partial view of the system. We report and discuss the comparative performance results with existing buffering approaches as well as random buffering which serves as a benchmark. We present separate evaluations of bufferer selection and gossip-based data dissemination. Reliability, content dissemination time, message delay, buffering delay, and minimum buffer requirements are considered as the key metrics investigated through simulations. The performance of our approach in the case of multiple senders, link failures with multiple bufferers, and scalability to larger networks are investigated. Several power-law and hierarchical overlay topologies are considered. Analytical bounds for reliability of dissemination are also provided.
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    ProFID: practical frequent item set discovery in peer-to-peer networks
    (Springer Nature, 2010) N/A; Department of Computer Engineering; N/A; Özkasap, Öznur; Çem, Emrah; Faculty Member; PhD Student; Department of Computer Engineering; College of Engineering; Graduate School of Sciences and Engineering; 113507; N/A
    This study addresses the problem of discovering frequent items in unstructured P2P networks. We propose a fully distributed Protocol for Frequent Item set Discovery (ProFID) where the result is produced at every peer. We also propose a practical rule for convergence of the algorithm. Finally, we evaluate the efficiency of our approach through an extensive simulation study on PeerSim.